1. Technical Field
The present invention relates generally to the treatment of drilling fluids, and more specifically, to a method and apparatus for treating hydrocarbon-contaminated cuttings removed from drilling mud so that the cuttings are made environmentally acceptable while the hydrocarbon contaminants are contemporaneously captured and returned for reuse in the drilling mud.
2. Background
In the conventional rotary drilling of oil wells, gas wells, and similar boreholes, a drilling derrick is mounted on a platform for drilling a well into the substratum. A drill pipe having a drill bit at its lower end is connected to a rotary table and draw works associated with the derrick. A drilling fluid is continuously pumped down through the middle of the drill pipe into the bottom of the borehole and through the drill bit. The fluid eventually returns to the surface, passing upwardly through the annulus defined by the rotating drill string and the borehole. As the drill bit cuts into the earth, the drill cuttings are carried by the fluid to the surface.
The drilling fluid, referred to as "mud," serves several functions, the most important of which includes cooling and lubricating the bit and removing drilled solids, or cuttings, from the borehole. While it is essentially a water based, flowable composition, the drilling mud is frequently compounded with a lubricant material such as diesel, crude oil, or another non-water soluble petroleum based constituent to facilitate the mud's lubricating characteristics.
The mud is usually contained in a mud pit, which is connected by way of a mud line and mud pump to a hose and swivel used to inject the mud into the top of the drill pipe. The returning mud, combined with cuttings, is captured in a mud return pipe. For obvious reasons, it is advantageous to recirculate the drilling mud through the drill pipe.
Recirculation of the mud becomes problematic, however, when the concentration of drill cuttings in the mud rises too high. In order for the drilling mud to perform its several functions, its viscosity, density and other properties must be maintained within acceptable limits. If permitted to accumulate in the system, the drill cuttings adversely affect these properties, reducing the carrying capacity of the mud and damaging drilling equipment, among other things.
To allow for effective recirculation, the mud may be separated from the cuttings prior to being recycled through the drill string. The cuttings are then disposed of as waste. Unfortunately, in the situation where the lubricating properties of the mud have been improved by the addition of hydrocarbons, the cuttings are contaminated, having been mixed with, and coated by, the hydrocarbons commingled in the mud. This presents a hazardous waste problem. Historically, the hydrocontaminated cuttings were diluted by mixing and hauled to remote sites for disposal in landfills.
Decontaminating the cuttings has known advantages. Treatment processes heretofore available to remove oil or other hydrocarbons from cuttings include distillation, solvent washing, and mud burning. While these processes are effective to varying degrees at stripping the hydrocarbon contaminants from cuttings, rendering the cuttings environmentally clean, they remain problematic in that a disposal problem persists with respect to the liquid or vapor form of the disassociated contaminant.
It is an object of this invention to improve the treatment of drilling mud to render environmentally safe, disposable drill cuttings, while contemporaneously capturing, controlling and recycling the disassociated hydrocarbon contaminants.
It should be understood, however, that although the invention is particularly useful in remediating drilling fluids, as described above, it is in no way limited to this application. The invention is also effective in the remediation and reclamation of a broad spectrum of petrochemical contaminants and hydrocontaminated soils. The invention may be used to remediate oil contaminated soil around tank batteries and refineries, as well as cleaning spills due to pipe line breaks or tanker truck accidents. Soil around military installations and rig-up yards may also be remediated by the present invention, as well as former drilling sites. The invention can also be used to prepare old filling station locations, refineries and industrial sites for full remediation.